Is there any software out there at allows you to design a new church building? Something that will let you do 2D and 3D? I have used Google Sketchup, but was not sure if there was a program out there that is easier to use. Perhaps some sort of home remodel software?

yeah... AutoCAD. It's expensive and hard to use. Those home remodel software things are really not useful for doing much more than just one room or so. If you're actually looking at building/designing a new church building you should hire an architect.

I designed, permitted and built an addition to our house (you can read about it on my home improvement blog, DIY Insanity). I used Home Design Pro, which is made by Chief Architect (makers of full-blown pro architecture software) but sold under the Better Homes and Gardens label. I tried some others, but Home Design Pro was the one that did what I needed without costing 4 figures.

That said, if you're just looking to get some ideas, Google Sketchup is about the easiest design software to use. If you're looking to design, permit and build a new building, hiring an architect as others have suggested is probably the way to go.

as a way of building a decent mock up, any of these will do. An local professional, however, will anticipate things such as minimum number of bathrooms, ADA requirements (bathrooms, ramps, hall/door widths, etc), electrical service locations/number/ratings, etc-all of which obviously affect floor layouts and the overall size of the building.

Churches are usually considered commercial buildings and would be designed by an Architect and Engineers. There is a lot more to designing these facilities than simply creating some drawings, if nothing else issues such as zoning ordinance and code compliance typically must be addressed. And try getting a permit for commercial construction without drawings stamped by registered Architects and Engineers, that usually is not going to happen. Sorry if this sounds dismissive, but I've been involved in too many projects where I was brought in for acoustics or audio/AV and when I first looked at the floor plans I had to start asking things like where the electrical and mechanical rooms were, where rated walls were and so on. It is a real pain to develop a nice concept and get everybody excited and then have to go back and almost start over once you realize all the required things that aren't shown but have to be accommodated.

If you are just trying to get some conceptual ideas down the SketchUp is hard to beat.

If you need or want 3D, Acad will do it well, but be prepared to spend a fair bit of time doing it, a fair bit of money for it, and a fair bit of time getting up that learning curve. It's not bad, it just takes some getting used to. You'll find yourself typing the command "u" a lot (for undo).